PROJECT SUMMARY Over the past few years, there has been a significant surge in non-pharmaceutical fentanyl (NPF) related unintentional overdose fatalities in multiple states across the U.S. Submitted in response to NIDA PAR- 16-055, Research Area 1 (Responses to sudden and severe emerging drug issues), this time-sensitive R21 application builds on interdisciplinary collaboration between researchers at the Center for Interventions, Treatment and Additions Research, the Department of Chemistry, Montgomery County Coroner's Office/Miami Valley Regional Crime Lab (MCCO/MVRCL) and Public Health-Dayton & Montgomery County. The overall purpose of the proposed study is to characterize NPF outbreaks through the integration of ethnographic/qualitative assessment of active user knowledge and experiences of NPF use, and the results from forensic analyses conducted by the postmortem toxicology and crime laboratories at MCCO/MVRCL. The study will be conducted in the Dayton Area (Montgomery County, Ohio), that has been recognized as a ?new frontier? of the U.S. heroin epidemic, and the place of one of the largest NPF outbreaks in the country. The Specific Aims of the study are to: 1) Provide an in-depth understanding of active user knowledge and experiences related to the availability and use of NPF products. 2) Analyze forensic data to characterize toxicological features and epidemiological trends of NPF use. 3) Compare, contrast, and integrate ethnographic and forensic perspectives on NPF outbreaks. The proposed study is significant because it will provide new information about toxicological features of the outbreaks and user knowledge, attitudes and behaviors related to NPF use. The key innovation is the interdisciplinary collaboration to integrate ethnographic and forensic perspectives.